1. Field of the Invention
This invention relates to a device and method for separating chaff from grain through the use of an electrostatic force.
2. Description of the Related Art
Several patents have utilized electric force in conjunction with the separation of impurities from grain.
U.S. Pat. No. 224,719 of Thomas B. Osborne is explicitly directed to removing contaminants from ground grain. In lines 17 through 21 of page 1, the Osborne patent states, "This invention relates to an improvement in devices for purifying ground grain, such as wheat, &c., the object being to remove all the particles which depreciate the quality of the flour . . . " claim 1 of the Osborne patent, moreover, is directed to the "process herein described for purifying flour . . . ."
Removing contaminants from ground grain is, however, technologically far different from removing chaff from grain as part of the harvesting process. And basic health concerns would dictate the preference for removing chaff prior to grinding the grain.
Secondly, it does not appear that "electrostatic separation" would be appropriate terminology for the technique of Mr. Osborne; and, indeed, U.S. Pat. No. 224,719 does not utilize such terminology. In the device of that patent, as stated on lines 54 through 63 of page 1, "Longitudinally over the receiver several rolls . . . are arranged parallel with each other and connected to the driving-shaft by bevel-gears . . . so as to be revolved . . . . These rolls run near the surface of the ground material in the receiver, and they are made from, or their surfaces coated with, hard rubber or equivalent material capable of being electrified or to present and electrified surface." Continuing on lines 64 through 82 of page 1, U.S. Pat. No. 224,719 provides, "Above each roll, or at some point above the receiver, is a pad . . . presenting to each roll, and so as to bear upon it, a cushion or surface of wool or equivalent material which will generate more or less electricity in consequence of the hard rubber rubbing against the said cushion, and giving to the rolls an electrified surface and an attractive power which will take from the surface of the ground material the lighter particles, such particles rising and attaching themselves to the rolls by the attractive power thus generated, and, adhering to the rolls, they ride upon the surface until they strike the cushion . . . above, or some other obstruction, then, being detached, will drop into troughs . . . below, which are in such relative position to the rolls as to catch the particles when they drop therefrom. The said troughs extend over the receiver parallel with the rolls."
Professors Dale R. Corson and Paul Lorrain, in their textbook Introduction to Electromagnetic Fields and Waves, W. H. Freeman and Company (1962), on page vii declare, "The first chapter deals with vector analysis in Cartesian, orthogonal curvilinear, cylindrical, and spherical coordinates. The following three chapters then cover electrostatic fields, first in a vacuum, and then in dielectrics." At the beginning of Chapter 5, on page 176, they state, "Our discussion of electromagnetic field theory has been limited so far to the effects of charges at rest." Consistently, "electrostatics" is defined as "[t]he study of the properties of electric charges at rest," on page 834 in volume 2 of the Encyclopaedic Dictionary of Physics, The MacMillan Company, Pergamon Press (1961), J. Thewlis, editor-in-chief.
In his textbook Classical Electrodynamics, John Wiley & Sons (1962), on page 1, Professor John David Jackson, however, provides a slightly different definition: "We will begin our discussion with the subject of electrostatics--problems involving time-independent electric fields." This second definition appears to find some support on page 103 of Classical Electromagnetic Radiation, Academic Press (1965), where Professor Jerry B. Marion comments, "In the preceding chapters we have discussed the mathematical description of static electric and magnetic fields . . . . We now wish to consider the more general situation in which the field quantities may depend upon the time."
Clearly, the charges in Osborne's rolls are moving. Furthermore, since the only method disclosed for causing the rolls to rotate is a hand-operated crank, the rotational motion of the rolls is unlikely to be uniform and would, therefore, create a time-dependent electromagnetic field.
Thirdly, the device of Osborne's U.S. Pat. No. 224,719, as portrayed in the drawings, the Osborne invention would not work. The troughs, N, actually touch the rolls, I, so that any light material attracted to a roll, I, would be scraped from the roll by the bottom of the trough, N. Furthermore, even if the light material could evade the trough, the placement of the pad, L, with respect to each roll, I, would tend to cause any light material displaced from the roll, I, by the pad, L, to fall back upon and be attracted again to the roll, I.
U.S. Pat. No. 4,534,856 to Louis C. Weiss and Devron P. Thibodeaux involves a set of parallel electrodes encased in a plastic panel upon which items to be separated, such as chaff from wheat fragments, are placed and charged. The voltage is then increased to effect levitation of the items and separation by means of an undulating traveling wave electric field. In fact, on lines 14 through 17 of column 3, Weiss' patent states, "In the Masuda-type travelling-wave apparatus, parallel sets of individual conductors connected to an A.C. electrical source form an undulating electric field in the surrounding air." The patent continues, on lines 26 through 30 of column 3, "If three phases of an A.C. voltage are connected successively to the different conductors, a series of traveling electric-waves are created. Material within the field is carried along as if on an invisible conveyor."
Certainly, under either definition, Weiss' invention is not an electrostatic process. As a matter of fact, Weiss' patent is entitled "Electrodynamic Method for Separating Components."
U.S. Pat. No. 1,355,477 of Sylvester S. Howell does apparently utilize an electrostatic system; but it merely enhances the separation of chaff from grain through the traditional process of winnowing, i.e., blowing air through the mixed grain and chaff, rather than providing an electrostatic method which can, by itself, perform the separation. There is an upper plate that is parallel to a lower plate. Particles placed upon the lower plate are charged, and some of these particles (presumably the chaff) are attracted toward the upper plate and thereby lifter from the lower plate. A stream of air is then blown between the plates to effect the separation.
And several patents, such as U.S. Pat. No. 4,116,822 of Clyde B. Webb, discharge material to be separated by electrical forces directly onto a rotating drum and then use electrical forces to causes different types of material to be discharged from the surface of the drum at different positions.